ABSTRACT
In Chapter 4, polymeric viscosity modifiers (improvers) were shown to lower the dependence of lubricant viscosity on temperature, thus enabling the development of multi-grade lubricants. A practical consequence of formulating with high molecular weight polymers is the expectation that a certain amount of permanent viscosity loss will occur during use, depending upon the polymer’s shear stability index. As long as the fluid maintains a minimum level of viscosity over its expected life, the tribological system should be adequately protected against premature wear, assuming the other performance additives remain active. Thus, degradation of polymer molecular weight is an important subject; and the development of mathematical models of polymer degradation is presented in Chapters 6 and 7.
